CN103323426A - Threshold laser liquid turbidity measuring device and method - Google Patents
Threshold laser liquid turbidity measuring device and method Download PDFInfo
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- CN103323426A CN103323426A CN2013102442416A CN201310244241A CN103323426A CN 103323426 A CN103323426 A CN 103323426A CN 2013102442416 A CN2013102442416 A CN 2013102442416A CN 201310244241 A CN201310244241 A CN 201310244241A CN 103323426 A CN103323426 A CN 103323426A
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Abstract
The invention discloses a threshold laser liquid turbidity measuring device and method. The measuring device comprises a light source module, a light path transmission and photovoltaic conversion module, a signal conditioning module, a signal acquisition and processing module, a controlled signal generating module, a flange, an optical focalizer and standard liquid. The measuring method comprises the following steps of: carrying out high speed modulation on a laser by a pulser in the controlled signal generating module, calculating transmission time of pulsed light in optical fibers, filtering direct current interference wave by a band-pass filtering circuit, filtering interference signals with same frequency and different time in the manner that an adjustable delayer controls the opening and closing of a threshold circuit, and selecting useful signals, thus realizing the accurate measurement on liquid turbidity. The measuring device provided by the invention has the advantages that the structure is simple, the stability is high, the realization is easy, the liquid turbidity measurement accuracy and sensitivity are effectively improved, and the technical guarantee for on-line water quality monitoring is provided.
Description
Technical field
The present invention relates to a kind of thresholding formula laser liquid turbidity meter and measuring method, belong to the environmental monitoring technology field.
Background technology
Along with industrial, the agriculture development of China, a large amount of industrial and agricultural wastewater, sewage discharge to rivers,lakes and seas, simultaneously, 80% unprocessed direct discharging is approximately arranged in China's city domestic sewage, samll cities and towns and vast domestic sewage in rural areas by using are in unordered emissions status especially, and this is so that the water quality deterioration in many areas.It is healthy that these have threatened people, becomes one of main Environmental Problems of puzzlement Economic Sustainable Development of China.Therefore need badly water quality is carried out real time on-line monitoring, for environmental improvement department provides foundation and reference.Turbidity is one of water quality five parameters, is an important indicator of Water Pollution Monitoring and body eutrophication.Therefore, the accurate measurement of water turbidity all has very important significance for the development of monitoring water environment, culture fishery and drinking water safety etc.
The measurement of external liquid turbidity since the thirties in last century just, formed sizable research and development, production scale and industrial chain.For example U.S. HACH company is in the 2100A type laboratory turbidimeter of release at the end of the eighties, use tungsten sodium lamp as light source, measurement range is 0-1000NTU, measuring accuracy to 0.01, the end of the nineties, company released again four sections of Novel laboratory turbidimeters, all adopted a plurality of silicon photo diodes for receiving beam, receiving scattered light signal from different perspectives, thus improved measurement range [1-4]; The CUS31/41 type turbidimeter that Germany E+H company releases is online high-end turbidity probe tip, and indoor design has two to survey optical channel, a channel measurement 90 degree scattered lights, and another channel measurement forward scattering light, measurement range is 0-9999NTU, precision can reach 0.01[5]; 7997 serial turbidimeters of Britain ABB KENT company have Four types: 7997-200 types are flow type, 90 degree scattering principles, and maximum range is 0-250NTU, minimum is 0-25NTU, 7997-201﹠amp; 202(202 is without washer) type is flow type, 90 degree scattering principles, low turbidimetry, maximum range is 0-30NTU, minimum is 0-1NTU, generally can be used for surveying turbidity less than the pure water of 1NTU; 7997-300 types are flow type, turbidimetry in the transmission. maximum range is 0-500NTU; 7997-400(405) types are immersion, and the high turbidimetry of transmission is applicable to open type pipeline and container and installs and uses, and maximum range is 0-1000NTU[6].The research of domestic turbidity detection technique is started late, and technical feature has been compared very large gap with external turbidimeter, and through nearly 10 years research of technique and Importing Foreign Advanced Technology experience, domestic turbidimeter parameters index improves a lot.For example Feihua, the Xiamen instrument company laboratory turbidimeter of having released TSZ series has been adopted the scattered light that many silicon photo diodes are surveyed multi-angle simultaneously, measurement range (0-4000NTU) and measuring accuracy (0.001) have been improved, measurement range is higher in the turbidimeter of laboratory at home, but it adopts tungsten lamp to make light source, optical design complicated [7]; The WT of Wuhan Water Company-online turbidimeter of OT3 series adopts the back scattering measuring principle, and uses optical fiber to realize transmission and the detection of light take infrared monochromatic light as light source, has eliminated the interference in the light path; Measurement range is 10-2000NTU,, measuring accuracy is 3%, is used for stream pipeline general formula and plug-in type and installs.The reception back scattering light signal that adopts so measurement lower limit is restricted (not meeting the ISO7027 standard), and is not measured the function of suspended solid, and measuring accuracy is compared abroad lower [8] with sensitivity.
At present, various turbidimetry system bulk both domestic and external is larger, be difficult to realize the particularly online turbidimetry under the mal-condition of small space, have again in domestic nephelometer, the precision of measuring all is difficult to compare with external product with sensitivity, thus design a kind of high precision, highly sensitive liquid turbidity measuring system is a key content of the present invention.
List of references:
[1]Hach Company,2100-N laboratory turbidimeter application instruction.
[2]Hach Company,2100-AN laboratory turbidimeter application instruction.
[3]Hach Company,2100-NIS laboratory turbidimeter application instruction.
[4]Hach Company,2100-ANIS laboratory turbidimeter application instruction.
[5]E+H Company,Cus31/41online turbidimeter application instruction.
[6]ABB-KENT Company,7997-200online turbidimeter application instruction.
[7] Feihua, Xiamen instrument company limited, TSZ serial experiment chamber turbidimeter instruction manual.
[8] Wuhan water instrument company, the WT-online turbidimeter instruction manual of OT3 series.
Summary of the invention
Fundamental purpose of the present invention provides a kind of thresholding formula laser liquid turbidity meter and measuring method, to solve precision and the low problem of sensitivity in the especially low turbidimetry technology of existing turbidimetry technology.
The technical solution used in the present invention is: a kind of thresholding formula laser liquid turbidity meter, comprise light source module 100, optic path and photoelectric conversion module 200, signal condition module 300, signals collecting and processing module 400, controllable signal generation module 500, the second flange 11B, optical fiber focuser 12, normal fluid 13; Light source module 100 comprises Laser Control System 101, laser instrument 102; Optic path and photoelectric conversion module 200 comprise three fiber port circulators 201, photodetector 202, the first flange 11A, three-flange 11C; Signal condition module 300 comprises pre-amplification circuit 301, second amplifying circuit 302, bandwidth-limited circuit 303, threshold circuit 304; Signals collecting and processing module 400 comprise signal acquisition circuit 401, controller 402, data display circuit 403, memory circuit 404; Controllable signal generation module 500 comprises adjustable time delay 501, pulse producer 502; Optical fiber focuser 12 is connected with three fiber port circulators 201 by the second flange 11B;
A. after described Laser Control System 101 was modulated through pulse producer 502, control laser instrument 102 was launched cycle and the adjustable light modulated 20 of pulsewidth, and described laser instrument 102 adopts the high-speed pulses modulation, and minimum pulse width is wanted to reach 10ps;
B. described laser instrument 102 utilizing emitted lights enter into three port circulators, 201 first port 201A through the first flange 11A, then the second port 201B from three port circulators 201 is transferred to optical fiber focuser 12 through the second flange 11B, from the illumination of optical fiber focuser 12 outgoing to normal fluid 13, part rear orientation light after normal fluid 13 endoparticle thing scatterings feeds back to optical fiber focuser 12, enter into three fiber port circulators 201 by the second flange 11B, and entering into photodetector 202 from the 3rd port 201C of three fiber port circulators 201 through three-flange 11C, photodetector 202 realizes that light signals are to the conversion of low current signal;
C. the low current signal of 301 pairs of photodetectors of described pre-amplification circuit, 202 conversions carries out electric current to conversion and the amplification of voltage, 302 pairs of pre-amplification circuit 301 output signals of second amplifying circuit are carried out secondary and are amplified, satisfy signal acquisition circuit 401 voltage range 30A-the 10V-+10V requirement, bandwidth-limited circuit 303 realizes that pulse producer 502 produces passing through of frequency signal, the signal amplitude that is different from the pulse producer frequency is subject to large decay or suppresses 30B, threshold circuit 304 can realize that normal fluid 13 rear orientation lights are produced signal 33 to be selected, to having with the asynchronous interchange undesired signal 31 of frequency, 32,35 isolate 30C);
D. described signal acquisition circuit 401 realizes that simulating signal is to the conversion of digital signal, controller 402 realizes that the control, digital signal processing, magnitude of voltage of Acquisition Circuit 401 are to the conversion of actual liquid turbidity, memory circuit 404 storage voltage values are to the coefficient of actual liquid turbidity conversion, and data display circuit 403 shows the turbidity value of liquid;
E. described adjustable time delay 501 is synchronous with pulse producer 502 signals, described adjustable time delay 501 sends enable signal and starts threshold circuit 304 behind time-delay Δ t1, threshold circuit 304 is opened, this moment, the signal from bandwidth-limited circuit 303 began to be selected, after opening the Δ t2 time, signal electing is complete, and threshold circuit 304 cuts out, 304 down periods of threshold circuit, all be isolated from the signal of bandwidth-limited circuit 303.
The transmission medium of light adopts single-mode fiber in described optic path and the photoelectric conversion module 200, have advantages of long transmission distance, loss is low, antijamming capability is strong, safe.
Described optic path and photoelectric conversion module 200 adopt the detecting structure of full optical fiber type, and probe size is less, and the liquid turbidity that is fit to small space is measured.
A kind of thresholding formula laser liquid turbidimetry method, performing step is as follows:
A. light is issued to accurate liquid 13 up to standard from laser instrument 102, is a fixed amount T by the transmission time of liquid-scattering arrival photodetector 202 then;
B., it is that T1 and cycle are the waveform 20 of T2 that pulse producer 502 generation width are set, and the time-delay that adjustable time delay 501 is set is Δ t1=T, and delay time length is Δ t2=(2～3) * T1;
C. 302 output waveform 30A of the second amplifying circuit in the signal conditioning circuit 300 comprise three parts in output waveform 30A: exchange undesired signal, its frequency is identical with the modulating light frequency of pulse producer 502 generations; Direct current undesired signal 34 all exists in whole cycle T 2; The voltage waveform 33 of the rear orientation light conversion that normal fluid 13 produces;
D. the output signal of second amplifying circuit 302 is by the output waveform 30B behind the bandwidth-limited circuit 303, and direct current interference wave 34 is filtered out, and exchanges undesired signal 31,32,35 and still exists;
E. adjustable time delay 501 is behind time-delay Δ t1, send enable signal to threshold circuit 304, threshold circuit 304 is opened, after opening the Δ t2 time, threshold circuit 304 cuts out, the voltage waveform 33 of the rear orientation light conversion that the normal fluid 13 of selecting produces is the magnitude of voltage of normal fluid 13 rear orientation lights conversion, exchanges undesired signal 31,32,35 and is isolated;
G. for the standard solution of different turbidity, measure the magnitude of voltage that its scattered light produces, the data of magnitude of voltage and standard solution turbidity carried out least-squares algorithm linear fitting, obtain the relation of turbidity and magnitude of voltage:
y=kx+b （1）
Wherein: x: magnitude of voltage, the mV of unit;
Y: titer turbidity value, the NTU of unit;
K, b: least-squares algorithm linear fitting coefficient;
H. fitting coefficient is saved in memory circuit (404), when measuring liquid turbidity, the magnitude of voltage that obtains is updated in the formula (1), obtain the liquid turbidity value.
Principle of the present invention: a kind of thresholding formula laser liquid turbidity meter and measuring method, comprise light source module, optic path and photoelectric conversion module, signal condition module, signals collecting and processing module, controllable signal generation module, flange, optical fiber focuser, normal fluid, as shown in Figure 1.Light source module comprises Laser Control System and laser instrument, for generation of the light of certain frequency and pulsewidth, as shown in Figure 2; Optic path and photoelectric conversion module comprise three fiber port circulators, photodetector, flange, be used for the transmission of light path and light to the conversion of electric signal, be specially three fiber port circulators the first port and receive the light of launching from laser instrument, and pass through the second port transmission to the optical fiber focuser, the optical fiber focuser shines on the normal fluid after light is focused on, enter into again the optical fiber focuser through the light after the normal fluid back scattering, the 3rd port by three fiber port circulators enters into photodetector, and photodetector realizes that light signal is to the conversion of low current signal; The signal condition module comprises pre-amplification circuit, second amplifying circuit, bandwidth-limited circuit and threshold circuit, be used for low current signal to the conversion of voltage signal, amplify and processing, being specially the pre-amplification circuit core devices is low noise, the high input impedance direct current amplifier, realization is to conversion and the amplification of low current signal, as shown in Figure 3A, second amplifying circuit carries out secondary to the pre-amplification circuit output signal and amplifies, satisfy the requirement of signal acquisition circuit voltage range, passing through of the frequency waveform that bandwidth-limited circuit realization pulse producer produces, other frequency signal amplitude attenuation or inhibition are shown in Fig. 3 B, threshold circuit is the key component of whole system, its quality is directly connected to precision and the sensitivity of system, the main signal that the normal fluid rear orientation light is produced of realizing is selected, to other same frequency but have the signal isolation at certain hour interval, shown in Fig. 3 C.The start-up time delay of threshold circuit needs to determine according to the transmission time of whole light path, need the effective acting time of threshold circuit to determine according to the pulsewidth that pulse producer produces, generally get 2～3 times pulsewidth, need the start-up time delay of threshold circuit and effective acting time precisely to determine, otherwise can select garbage signal to isolate useful signal; Signals collecting and processing module comprise signal acquisition circuit, controller, data display circuit, memory circuit, the digital filtering that is used for signal is processed, magnitude of voltage is to the conversion of turbidity value, data storage and demonstration, be specially signal acquisition circuit and realize that simulating signal is to the conversion of digital signal, control, digital signal processing, the collection magnitude of voltage of controller realization Acquisition Circuit are changed to the actual liquid turbidity, data display circuit shows the turbidity value of liquid, and the memory circuitry stores magnitude of voltage is to actual liquid turbidity conversion parameter and liquid turbidity value; Controllable signal generation module comprises adjustable time delay, pulse producer, be used for the modulated laser light that produces and the break-make of controlling threshold circuit, be specially pulse producer by the radiative pulsewidth of modulated laser and frequency, adjustable time delay and pulse producer are synchronous, the break-make of control threshold circuit; Standard solution for different turbidity, measure the magnitude of voltage that its scattered light produces, the data of magnitude of voltage and standard solution turbidity are carried out least-squares algorithm linear fitting, obtain the linear relationship of turbidity and magnitude of voltage, and fitting coefficient is saved in the memory circuit, when measuring liquid turbidity, the magnitude of voltage that obtains is updated in the relational expression, obtains the liquid turbidity value.
The present invention's beneficial effect compared with prior art is:
(1) optical system of the present invention can be come the luminous pulsewidth of dynamic modulation laser instrument and cycle by pulse producer, and determine the break-make of adjustable time delay control threshold circuit by the time of calculating optic path, thereby the signal that the fluid to be measured scattered light produces is selected, greatly improved the measuring accuracy of system;
(2) Optical Maser System adopts the high-speed pulse modulation in the optical system of the present invention, avoids environment temperature and pressure to change and causes the random variation of laser phase, thereby reduce external interference, has improved Systems balanth;
(3) optical transmission medium of the present invention adopts single-mode fiber, have advantages of long transmission distance, loss is low, antijamming capability is strong, safe;
(4) bandwidth-limited circuit in the signal conditioning circuit of the present invention can carry out effective filtering to dc noise signal and the signal that is different from modulating light frequency, has greatly improved the measuring accuracy of system;
(5) threshold circuit in the signal conditioning circuit of the present invention can be to having same frequency with light modulated, but and light modulated have the signal at certain hour interval to shield, the reflected light of end face of flange for example, the reflected light of three port circulators.This threshold circuit can effectively catch the signal that the liquid rear orientation light produces, even effective seizure of single photon, so can significantly improve measuring accuracy and sensitivity;
(6) the present invention adopts the detecting structure of full optical fiber type, and probe size is less, and the liquid turbidity that is fit to small space is measured.
Description of drawings
Fig. 1 is liquid turbidity measuring system schematic diagram of the present invention;
Fig. 2 is the schematic diagram of modulating pulse light of the present invention;
Fig. 3 A is of the present invention through signal schematic representation behind the two-stage amplifying circuit;
Fig. 3 B is of the present invention through signal schematic representation behind the bandwidth-limited circuit;
Fig. 3 C is of the present invention through signal schematic representation behind the threshold circuit;
Fig. 4 is least-squares algorithm linear fitting schematic diagram of the present invention.
Embodiment
Below in conjunction with accompanying drawing enforcement of the present invention is described in further detail.
Fig. 1 is a kind of thresholding formula laser liquid turbidity meter schematic diagram, comprises light source module 100, optic path and photoelectric conversion module 200, signal condition module 300, signals collecting and processing module 400, controllable signal generation module 500, the first flange 11A, the second flange 11B and three-flange 11C, optical fiber focuser 12, normal fluid 13.Light source module 100 comprises Laser Control System 101 and laser instrument 102, and Laser Control System 101 is controlled later on laser instrument 102 by pulse producer 502 modulation and launched the light of certain frequency and pulsewidth; Optic path and photoelectric conversion module 200 comprise three fiber port circulators 201, photodetector 202, the first flange 11A, be used for the transmission of light path and light to the conversion of electric signal, be specially three fiber port circulators, 201 first port 201A and receive the light of launching from laser instrument 102, and be transferred to optical fiber focuser 12 by the second port 201B, after focusing on, 12 pairs of light of optical fiber focuser shine on the normal fluid, through entering into optical fiber focuser 12 after the normal fluid back scattering, the 3rd port 201C by three fiber port circulators 201 enters into photodetector 202, photodetector 202 realizes that light signal is to the conversion of low current signal, what wherein three fiber port circulators 201 adopted is the polarization irrelevant optical circulator, has high-isolation, the advantage of low insertion loss and high return loss, be specially maximum insertion≤0.8dB, minimum isolation 〉=40dB, return loss 〉=50Db, the optical fiber focuser has low insertion loss, the advantage of minimum echo loss, it has the function of receiving and dispatching in one, can either Emission Lasers to normal fluid, also can receive the backward scattered light of normal fluid, photodetector 202 adopts high sensitivity avalanche optoelectronic detecting module, its objective is and can detect the even intensity of single photon of faint scattered light; Signal condition module 300 comprises pre-amplification circuit 301, second amplifying circuit 302, bandwidth-limited circuit 303 and threshold circuit 304, be used for low current signal to the conversion of voltage signal, amplify and processing, being specially pre-amplification circuit 301 core devices is low noise, the high input impedance direct current amplifier, realization is to conversion and the amplification of low current signal, 302 pairs of pre-amplification circuit output signals of second amplifying circuit are carried out secondary and are amplified, satisfy the requirement of signal acquisition circuit voltage range-10V-+10V, bandwidth-limited circuit 303 realizes that pulse producer produces passing through of frequency waveform, other frequency signal amplitude attenuation or inhibition, threshold circuit 304 is key components of whole system, the main selection that realizes the normal fluid rear orientation light is produced signal is to other same frequency but have the isolation of the signal at certain hour interval.The start-up time delay of threshold circuit 304 needs to determine according to the transmission time of whole light path, need the effective acting time of threshold circuit to determine according to the pulsewidth that pulse producer produces, generally get 2-3 pulsewidth doubly, need the start-up time delay of threshold circuit and effective acting time precisely to determine, otherwise can select garbage signal to isolate useful signal; Signals collecting and processing module 400 comprise signal acquisition circuit 401, controller 402, data display circuit 403, memory circuit 404, the digital filtering that is used for signal is processed, magnitude of voltage is to the conversion of turbidity value, data storage and demonstration, be specially signal acquisition circuit 401 and realize that simulating signal is to the conversion of digital signal, controller 402 is realized the control of Acquisition Circuit, digital signal processing, gathering magnitude of voltage changes to the actual liquid turbidity, data display circuit 403 shows the turbidity value of liquid, and memory circuit 404 storage voltage values are to actual liquid turbidity conversion parameter and liquid turbidity value; Controllable signal generation module 500 comprises adjustable time delay 501, pulse producer 502, the break-make that is used for modulated laser and control threshold circuit, be specially pulse producer 502 by the light of the modulated laser 102 certain pulsewidths of emission and frequency, adjustable time delay 501 is synchronous with pulse producer 502 signals, is used for the break-make of control threshold circuit 304.
Fig. 2 is the modulation signal schematic diagram that pulse producer produces.Its effect is the light that the control Optical Maser System produces certain frequency and pulsewidth; Modulating frequency f2=1/T2 wherein, the size of modulating frequency is determined at the transmission time of optical fiber T according to light, generally gets T2 〉=1.5-2T, in order to avoid utilizing emitted light and scattered light produce interference in Optical Fiber Transmission.For example laser instrument is L1 to the transmission range of the light of normal fluid, and normal fluid is L2 to the transmission range of the light of photodetector, and then light is issued to accurate liquid up to standard from laser instrument, is a fixed amount T by the transmission time of liquid-scattering arrival photodetector then;
Fig. 3 A is the output waveform schematic diagram of the second amplifying circuit in the signal conditioning circuit.Wherein the 31,32, the 35th, exchange interference wave, result from the reflection of connectivity port, frequency is identical with the modulating light frequency that pulse producer produces, direct current interference wave 34, generation and parasitic light or be surround lighting all exist in whole cycle T 2, the magnitude of voltage that the rear orientation light that waveform 33 produces for normal fluid is changed, the modulating light frequency that frequency and pulse producer produce is identical, and waveform 31,32,33,35 frequencies are identical, but have certain time interval;
Fig. 3 B is the waveform schematic diagram of bandwidth-limited circuit output.Bandwidth-limited circuit filters out the waveform different with modulating light frequency, and the clutter of the less filtering of bandwidth is cleaner, but filtering circuit is required also higher, and direct current interference wave 34 is filtered out, exchange undesired signal 31,32,35 and waveform 33 still exist;
Fig. 3 C is the waveform schematic diagram of the output of threshold circuit.Adjustable time delay 501 is behind time-delay Δ t1, send enable signal to threshold circuit, threshold circuit is opened, begin to catch the signal waveform that is produced by the normal fluid scattered light, after opening the Δ t2 time, threshold circuit cuts out, the waveform 33 that catches is the signal that the normal fluid scattered light produces, exchanging undesired signal 31,32,35 is isolated, Δ t1 is the opening time of gate circuit, and its start time and pulse producer are synchronous, and its size is transmitted into the time value T that light arrives photodetector for light, Δ t2 is the service time of gate circuit, and its numerical value is (2～3) * T1;
Fig. 4 is the least-squares algorithm linear fitting schematic diagram that standard solution turbidity value and voltage carry out.For the standard solution of different turbidity, measure the magnitude of voltage 40 that its scattered light produces, the data of magnitude of voltage and standard solution turbidity are carried out least-squares algorithm linear fitting, obtain the linear relationship 41 of turbidity and magnitude of voltage, fitting formula is:
y=kx+b
Wherein: x: magnitude of voltage, the mV of unit;
Y: titer turbidity value, the NTU of unit;
K, b: least-squares algorithm linear fitting coefficient;
Error:
e=|y1-（kx1+b）|
E is error size behind actual turbidity value and the process least square fitting, and its value size can be used as the evaluation of precision behind least square fitting.
The present invention is simple in structure, be easy to realize, stability is high, effectively improved liquid turbidity measuring accuracy and sensitivity, provides technical guarantee for carrying out long-term online water quality monitoring.
The content that is not described in detail in the instructions of the present invention belongs to the known prior art of this area professional and technical personnel.
The above only is preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (4)
1. thresholding formula laser liquid turbidity meter, it is characterized in that: comprise light source module (100), optic path and photoelectric conversion module (200), signal condition module (300), signals collecting and processing module (400), controllable signal generation module (500), the second flange (11B), optical fiber focuser (12), normal fluid (13); Light source module (100) comprises Laser Control System (101), laser instrument (102); Optic path and photoelectric conversion module (200) comprise three fiber port circulators (201), photodetector (202), the first flange (11A), three-flange (11C); Signal condition module (300) comprises pre-amplification circuit (301), second amplifying circuit (302), bandwidth-limited circuit (303), threshold circuit (304); Signals collecting and processing module (400) comprise signal acquisition circuit (401), controller (402), data display circuit (403), memory circuit (404); Controllable signal generation module (500) comprises adjustable time delay (501), pulse producer (502); Optical fiber focuser (12) is connected with three fiber port circulators (201) by the second flange (11B);
A. after described Laser Control System (101) is modulated through pulse producer (502), control laser instrument (102) is launched cycle and the adjustable light modulated (20) of pulsewidth, described laser instrument (102) adopts the high-speed pulse modulation, and minimum pulse width is wanted to reach 10ps;
B. described laser instrument (102) utilizing emitted light enters into three port circulators (201) first ports (201A) through the first flange (11A), then send and be transferred to optical fiber focuser (12) through the second flange (11B) from second port (201B) of three port circulators (201), from the illumination of optical fiber focuser (12) emission to normal fluid (13), part rear orientation light after the scattering of normal fluid (13) endoparticle thing is reflected back optical fiber focuser (12), enter into three fiber port circulators (201) by the second flange (11B), and entering into photodetector (202) from the 3rd port (201C) of three fiber port circulators (201) through three-flange (11C), photodetector (202) realizes that light signal is to the conversion of low current signal;
C. described pre-amplification circuit (301) carries out electric current to conversion and the amplification of voltage to the low current signal of photodetector (202) conversion, second amplifying circuit (302) carries out secondary to the output signal of pre-amplification circuit (301) and amplifies, satisfy the requirement of signal acquisition circuit (401) voltage range (30A)-10V-+10V, bandwidth-limited circuit (303) realizes that pulse producer (502) produces passing through of frequency signal, the signal amplitude that is different from the pulse producer frequency is subject to large decay or inhibition (30B), threshold circuit (304) can be realized the signal (33) that normal fluid (13) rear orientation light produces is selected, to having with the asynchronous interchange undesired signal (31 of frequency, 32,35) isolate (30C);
D. described signal acquisition circuit (401) realizes that simulating signal is to the conversion of digital signal, controller (402) realizes that the control, digital signal processing, magnitude of voltage of Acquisition Circuit (401) are to the conversion of actual liquid turbidity, memory circuit (404) storage voltage value is to the coefficient of actual liquid turbidity conversion, and data display circuit (403) shows the turbidity value of liquid;
E. described adjustable time delay (501) is synchronous with pulse producer (502) signal, described adjustable time delay (501) sends enable signal and starts threshold circuit (304) behind time-delay Δ t1, threshold circuit (304) is opened, this moment, the signal from bandwidth-limited circuit (303) began to be selected, after opening the Δ t2 time, signal electing is complete, and threshold circuit (304) cuts out, threshold circuit (304) down periods, all be isolated from the signal of bandwidth-limited circuit (303).
2. thresholding formula laser liquid turbidity meter according to claim 1, it is characterized in that: the transmission medium of light adopts single-mode fiber in described optic path and the photoelectric conversion module (200), have advantages of long transmission distance, loss is low, antijamming capability is strong, safe.
3. thresholding formula laser liquid turbidity meter according to claim 1 is characterized in that: described optic path and photoelectric conversion module (200) adopt the detecting structure of full optical fiber type, and probe size is less, and the liquid turbidity that is fit to small space is measured.
4. thresholding formula laser liquid turbidimetry method is characterized in that performing step is as follows:
A. light is issued to accurate liquid up to standard (13) from laser instrument (102), is a fixed amount T by the transmission time of liquid-scattering arrival photodetector (202) then;
B., it is T1 and cycle to be the waveform (20) of T2 that pulse producer (502) generation width is set, and the time-delay that adjustable time delay (501) is set is Δ t1=T, and delay time length is Δ t2=(2～3) * T1;
C. second amplifying circuit (302) output waveform (30A) in the signal conditioning circuit (300), in output waveform (30A), comprise three parts: exchange undesired signal (31,32,35), its frequency is identical with the modulating light frequency that pulse producer (502) produces; Direct current undesired signal (34) all exists in whole cycle T 2; The voltage signal (33) of the rear orientation light conversion that normal fluid (13) produces;
D. the output signal of second amplifying circuit (302) is by the output waveform (30B) behind the bandwidth-limited circuit (303), and direct current undesired signal (34) is filtered out, and exchanges undesired signal (31,32,35) and still exists;
E. adjustable time delay (501) is behind time-delay Δ t1, send enable signal to threshold circuit (304), threshold circuit (304) is opened, after opening the Δ t2 time, threshold circuit (304) cuts out, the voltage signal (33) of the rear orientation light conversion that the normal fluid (13) of selecting produces is the magnitude of voltage of normal fluid (13) rear orientation light conversion, exchanges undesired signal (31,32,35) and is isolated;
F. controller (402) gathers the magnitude of voltage of threshold circuit (304) output by signal acquisition circuit (401), and magnitude of voltage is done to be saved in memory circuit (404) behind maximum-minimum value removal and the average value processing;
G. for the standard solution of different turbidity, measure the magnitude of voltage that its scattered light produces, the data of magnitude of voltage and standard solution turbidity carried out least-squares algorithm linear fitting, obtain the relation of turbidity and magnitude of voltage:
y=kx+b （1）
Wherein: x: magnitude of voltage, the mV of unit;
Y: titer turbidity value, the NTU of unit;
K, b: least-squares algorithm linear fitting coefficient;
H. fitting coefficient is saved in memory circuit (404), when measuring liquid turbidity, the magnitude of voltage that obtains is updated in the formula (1), obtain the liquid turbidity value.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103528960A (en) * | 2013-10-25 | 2014-01-22 | 吉林省百瑞生科技发展有限公司 | Online monitoring system of sewage by spectral interference method |
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| CN106226213A (en) * | 2016-09-30 | 2016-12-14 | 天津市誉航润铭科技发展有限公司 | A kind of diesel particulate thing explosion-proof measurement sensor |
| CN106525961A (en) * | 2016-11-03 | 2017-03-22 | 中国海洋大学 | Method for detecting water turbidity through ultrasonic wave |
| CN110231311A (en) * | 2019-05-28 | 2019-09-13 | 中国地质大学（武汉） | A kind of portable fiber-optic turbidity detection device |
| CN110231311B (en) * | 2019-05-28 | 2023-12-01 | 中国地质大学（武汉） | Portable optical fiber turbidity detection device |
| CN113155743A (en) * | 2021-04-23 | 2021-07-23 | 中国科学院大学 | Turbidity measuring method and system based on quadrature signal modulation |
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